1. Field of the Invention
The present invention relates to a printer head for an ink jet printer, and more particularly to such a head incorporating piezoelectric drive elements.
2. Prior Art
Printing heads for ink jet printers typically contain several means for forming jets, constituting ink channels which run through the printing head. Such an arrangement is shown in the German Pat. No. 2,543,451. The individual ink channels converge in a ray-shapped fashion in the direction of a jet plate, having apertures aligned with the channels and which terminates the ink channels. Piezoelectric drive elements surround the ink channels in a cylindrical fashion toward the rear of the printing head. When the piezoelectric drive elements are energized, the printing fluid is ejected, drop-by-drop, through deformation of the piezoelectric drive elements. This construction permits the manufacture of the print head by means of casting the drive elements in place, while simultaneously forming the ink channels. However, a considerable expense is involved in producing the printing heads in this manner, since the casting must take place in a vacuum in order to satisfy the critical requirements of the internal surface of the ink channels. Furthermore, extreme precision is required in certain parameters such as the mixing ratio and the temperature of the casting compound, in order to form a printing head which is satisfactory. Even with these precautions, however, the interior surface of the ink channels are sometimes rough, and this can lead to interference in operation since the mechanical coupling between piezoelectric element and the ink channel is impaired by roughness, and bubbles of entrained air can collect in the smallest cavities of the ink channel. Also, the providing of electrical connections to the piezoelectric elements also present a problem during manufacturing, since these connections must be made prior to casting of the printing head.